Billionaire Tesla chief executive Elon Musk is leaving the Trump administration after leading a tumultuous efficiency drive, during which he upended several federal agencies but ultimately failed to deliver the generational savings he had sought.

His "off-boarding will begin tonight," a White House official said late on Wednesday, confirming Musk's departure.

Musk earlier in the day took to his social media platform X to thank President Donald Trump as his time as a special government employee with the Department of Government Efficiency (Doge) draws to an end.

His departure was quick and unceremonious. He did not have a formal conversation with Trump before announcing his exit, according to a source, who added that his departure was decided "at a senior staff level".

While the precise circumstances of his exit were not immediately clear, he leaves a day after criticising Trump's marquee tax bill, calling it too expensive and a measure that would undermine his work with Doge.

Some senior White House officials, including deputy chief of staff Stephen Miller, were particularly irked by those comments, and the White House was forced to call Republican senators to reiterate Trump's support for the package, a source said.

While Musk remains close to the president, his exit comes after a gradual, but steady slide in standing.

After Trump's inauguration, the billionaire quickly emerged as a powerful force in Trump's orbit: hyper-visible, unapologetically brash and unfettered by traditional norms. At the Conservative Political Action Conference in February, he brandished a red metallic chainsaw to wild cheers. "This is the chainsaw for bureaucracy," he declared.

On the campaign trail, Musk had said Doge would be able to cut at least US$2 trillion in federal spending. He did not hide his animus for the federal workforce, and he predicted that revoking "the Covid-era privilege" of telework would trigger "a wave of voluntary terminations that we welcome".

But some cabinet members who initially embraced Musk's outsider energy grew wary of his tactics, sources said. Over time, they grew more confident pushing back against his job cuts, encouraged by Trump's reminder in early March that staffing decisions rested with department secretaries, not with Musk.

Musk clashed with three of Trump's most senior cabinet members – Secretary of State Marco Rubio, Transportation Secretary Sean Duffy and Treasury Secretary Scott Bessent. He called Trump's trade adviser Peter Navarro a "moron" and "dumber than a sack of bricks".

At the same time, Musk began to hint that his time in government would come to a close, while expressing frustration at times that he could not more aggressively cut spending.

In an April 22 Tesla conference call, he signaled he would be significantly scaling back his government work to focus on his businesses. (Reuters)